RELATED APPLICATIONS
This application is related to U.S. Ser. No. 07/909,332, now U.S. Pat. No. 5,335,566, titled SHIFT CONTROL METHOD/SYSTEM, filed Jul. 6, 1992, and assigned to the same assignee, EATON CORPORATION, as this application.
1. Field of Invention
This invention relates to control methods and systems for determining vehicular gross combination weight (GCW), and to vehicular controls, such as anti-lock brake systems and transmission controllers utilizing current GCW as a control parameter. By way of example, the present invention relates to shift control methods/systems for automated mechanical transmissions wherein the likelihood of acceptably completing a selected upshift is evaluated in view of existing vehicle operating conditions, including GCW, and only acceptably completable shifts are initiated. An acceptably completable upshift is an upshift into a target ratio wherein, under existing vehicle operating conditions, the maximum available engine torque will cause at least a predetermined minimum vehicle acceleration. Current GCW also may be used for electronic braking systems, intelligent vehicle/highway systems, fleet management systems, etc.
This invention allows determination of GCW using existing information in an AMT system, preferably an AMT with an electronic engine, without adding any sensors or additional electronic or mechanical hardware.
2. Description of the Prior Art
Automated vehicular controls, such as fully or partially automatic transmission systems, both for heavy-duty vehicles, such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, transmission shaft speeds, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Examples of such transmission controls may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065; 4,361,060; 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
Another type of partially automated transmission system utilizes a semi-automatic shift implementation system/method for a mechanical transmission system for use in vehicles having a manually only controlled engine throttle means and/or a manually only controlled master clutch. The system usually has at least one mode of operation wherein the shifts to be semi-automatically implemented are automatically preselected. An electronic control unit (ECU) is provided for receiving input signals indicative of transmission input and output shaft speeds and for processing same in accordance with predetermined logic rules to determine (i) if synchronous conditions exist, and (ii) in the automatic preselection mode, if an upshift or downshift from the currently engaged ratio is required and to issue command output signals to a transmission actuator for shifting the transmission in accordance with the command output signals. Transmission systems of this general type may be seen by reference to U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; and 5,089,965, the disclosures of which are hereby incorporated by reference.
While the above-described automatic, semi-automatic and/or partial automatic shift implementation type vehicular mechanical transmission systems are well suited for their intended applications, they are not totally satisfactory as they will occasionally initiate an attempted shift, which, due to vehicle operating conditions, should not be completed. This is especially a concern for upshifts of automated mechanical transmission systems when the vehicle is operating against a particularly great resistance (usually associated with grade and/or load) and the engine, in the target ratio, is unable to accelerate or maintain vehicle velocity, which will result in undesirable "hunting" as the transmission undergoes cycles of upshifts followed by almost immediate downshifts.
It is known in the prior art to provide a shift control method/system for a vehicular at least partially automated mechanical transmission system which, upon sensing an automatic or manual selection of an upshift from a currently engaged gear ratio to a target gear ratio will, based upon currently sensed vehicle operating conditions and/or assumed constants, determine if the selected shift is feasible and acceptable (i.e., will the available engine torque applied to the drivewheels in the target ratio be sufficient to provide at least a predetermined minimum vehicle acceleration?) and initiate only feasible and acceptable shifts. Examples of such systems may be seen by reference to U.S. Pat. Nos. 5,241,476; 5,172,609; 4,823,646 and 5,272,939, the disclosures of which are incorporated herein by reference.
For vehicles of substantially constant GCW such as buses, mobile cranes, etc., assuming a vehicle equipped with an electronic data link, such as defined in SAE J 1922 and/or SAE J 1939 protocol, on which engine torque or a parameter indicative of engine torque may be sensed, upon determination that an upshift from a currently engaged ratio into a target ratio is desired, current engine torque and vehicle acceleration are sensed from which the controller can estimate the engine torque required, in the target ratio and at current vehicle operating conditions, to maintain the minimum acceptable vehicle acceleration. The system then proceeds to determine if the proposed shift is feasible/acceptable utilizing the logic discussed above. If the proposed shift (usually an upshift)is not acceptable, then the shift request may be modified (i.e., a skip shift request changed to single shift) or cancelled for a predetermined period of time (such as 10 seconds).
The prior art vehicular control systems utilizing GCW as a control parameter were not totally satisfactory, as a relatively simple and reliable method for determining current vehicular GCW for vehicles not having a substantially constant GCW was not provided. By way of example, a large truck or tractor-semitrailer vehicle may have a GCW ranging from about 10,000 pounds up to about 80,000 pounds or more, depending upon vehicle type and load.